1. Field of the Invention
This invention is related to stable mixtures containing opacifying pigments and more specifically, to stable mixtures containing select combinations and levels of titanium dioxide, a thickener, and a dispersant for use in making paint and other end products.
2. Description of Related Art
In co-pending U.S. provisional patent applications Ser. Nos. 60/183,655; 60/183,656; and 60/247,639; prepaints and a method of making paints from these prepaints is described. One of the prepaints is a mixture comprising at least one opacifying pigment, typically titanium dioxide. The other two prepaints may contain either an extender pigment or/and an emulsion polymeric binder. A key requirement for the prepaints is their compatibility with one another so that they may be mixed with each other in various ratios to make at least one paint line. Another key requirement is that the prepaints, whether comprising an opacifying pigment, an extender pigment, or an emulsion polymeric binder, be stable so that the prepaints may be prepared, shipped, and stored without failing, for example, failure by exhibiting non-homogeneity, syneresis, settling, gelling and/or viscosity changes.
With respect to prepaints containing an opacifying pigment, stability can be a serious problem. This is especially true when one considers that even the best commercially-available titanium dioxide slurries show some syneresis (>2% by volume by visual inspection) upon storage and must be stirred vigorously and for a considerable length of time before use.
Hence, there is a need for stable mixtures containing specific combinations and levels of titanium dioxide, thickeners, and dispersants that may be employed, inter alia, as prepaints in a method of making paints or as conventional components in other end-uses where opacifying pigments are employed, including coatings, impregnants, inks, graphic arts, papers, textiles, caulks, mastics, adhesives, sealants, building products and leather.